This invention relates generally to bicycle type apparatus and more particularly to bicycle type exercisers, although it may be equally applicable to the upwardly open type frame used on girls' and ladies' bicycles.
Two important factors in frame design for bicycle type exercisers are leg room and vertical stiffness.
Bicycle type exercisers are stationary but otherwise similar in many respects to bicycles and use some of the same parts. A frame similar to that on an upwardly open girls' or ladies' bicycle is often used, having twin, parallel, curved reach tubes. It provides ample leg room for older or overweight persons and those who are not athletically proficient to be seated in an exercising position without lifting a leg above a high bar. One example is shown in FIG. 1 of U.S. Pat. No. 3,664,027 issued May 23, 1972, to Albert J. Fritz and Rudolph L. Schwinn. A further example of that prior art construction is shown in FIGS. 5 and 6.
It is important to the comfort and well-being of the user that the frame be absolutely rigid and free from noticeable vertical deflection and sidewise whippiness in operation. In practice, this is difficult to achieve with the above-mentioned conventional upwardly open frame.
Many people who find bicycle type exercisers beneficial lack the athletic dexterity required to ride a real bicycle. Due to age, arthritis-stiffened joints, excess weight or other condition for which an exercise bike is recommended, a person may not be able to lift his or her leg very high off the floor to mount or dismount. Some who find it difficult or impossible to ride bicycles use bicycle type exercisers regularly. For them it is important that it be easy to mount and dismount. Maximum leg room is essential to prevent tripping on the frame. Unfortunately, increasing leg clearance above the chain guard by simply lowering the reach tube or making it with a smaller cross section reduces the vertical rigidity of the frame. This is well known to designers and manufacturers of this equipment.
Accordingly, prior to the present invention, attempts to increase leg clearance by moving the reach tube down toward the chain guard have always included a supplemental connection of some kind between the seat mast and handlebar head tube. A single reach tube without such a supplemental connection has never been considered practical.
The above-mentioned U.S. Pat. No. 3,664,027 with twin reach tubes is an example of designers' unwillingness to rely on a single reach tube. Each reach tube, in effect, acts as a supplemental stiffening strut for the other.
Other attempts to maximize leg room by an upwardly open frame below the seat, but using separate stiffening struts of one kind or another to obtain the desired vertical rigidity, are shown in Gustafson Design U.S. Pat. No. 275,589, Philbin U.S. Pat. No. 3,833,216 and Wolfa U.S. Pat. No. 3,995,491.